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Title: IRRADIATION-DERIVED SEX REVERSAL MUTANTS FOR CLONING SEX DETERMINATION GENES IN PAPAYA

Author
item YU, Q - HARC
item Moore, Paul
item SKELTON, R - HARC
item BLAS, ANDREA - HARC
item MING, R - UNIV ILLINOIS

Submitted to: International Congress of Plant Molecular Biology
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/2006
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Unlike most animals, most flowering plants are hermaphrodites possessing both male and female organs. Papaya (Carica papaya L.) is one of the few plant species that produce male, female, and hermaphrodite flowers on separate individuals. These variations have distinctive morphologies and sexual functions in a single species and serve as a useful model for investigating the genomics of sex determination in plants. Sex determination in papaya is controlled by a primitive Y chromosome, containing functional and degenerated genes that regulate sex organ development, inflorescence morphology, and embryo abortion. We have an NSF project to fully sequence the male-specific region of papaya’s Y chromosome (MSY) and its corresponding region on the X chromosome for obtaining sequence information necessary to characterize and clone genes controlling sex-determination. We used Co60 '-irradiation to mutate pollen within flower buds of the gynodioecious variety SunUp and the dioecious variety AU9 to produce Y deletion lines. Three mutants were found among nearly 5,000 plants derived from irradiated pollen. All three mutants were from the 5 krad treatment and had the long, pendulous, many flowered cymose inflorescence typical of male plants, but the flowers borne on the inflorescence were not the slender, anther bearing male flowers. One of the mutants exhibited typical female flowers with large functional pistils and no stamens, while the other two mutants showed bisexual hermaphrodite flowers. A total of 392 pairs of primers, were designed from five completely sequenced MSY BACs to cover about 580kb of the MSY region and used to amplify the genomic DNA from the mutant plants. The sequenced PCR products confirmed that all three mutants had the male Y chromosome sequences except for a few single nucleotide deletions. Analysis of the deletion lines is concurrent with sequencing of the MSY to focus attention to regions with candidate genes for sex-determination.